Protein in beer

FIGURE 2.4 Partial amino acid sequence of barley hordein (source of haze-active protein in beer) P = proline and Q = glutamine. 

Adsorbents that remove proteins or polyphenols are used to treat a number of beverages to delay the onset of haze formation. Protein adsorbents include bentonite and silica. Bentonite removes protein nonspecifically (see Fig. 2.19) and so is unsuitable for stabilizing beverages where foam is desirable (beer and champagne). Silica, on the other hand, has remarkable specificity for HA proteins while virtually sparing foam-active proteins in beer (Siebert and Lynn, 1997b) (see Fig. 2.20). Silica removes approximately 80% of the HA protein from unstabilized beer, while leaving foam-active protein nearly untouched at commercial treatment levels. 

FIGURE 2.21 Concept of silica binding to HA protein in beer. Reprinted with permission from Siebert and Lynn (1997b). Copyright 1997 American Society of Brewing Chemists. 

Chillproofing of Beer. In chillproofing of beer, proteolytic enzymes, primarily papain, are used to hydrolyze the proteins in beer contributed by the grain, malt, and yeast. The process must be controlled so that the polypeptides produced are no longer able to form an insoluble precipitate... 

Cleaves high molecular weight protein in beer... 

The basic raw materials for the production of beer are sweet worts formed by en2ymatic hydrolysis of cereal starches. The principal cereal is barley which, after malting, is also the source of en2ymes that hydroly2e starches, glucans, and proteins. In some countries, eg, Germany, the mash biH consists... 

Caramel color can be made with either positively or negatively charged particles. This allows manufacturers to use negative colloidal caramel in acidic soft drinks, and positive colloidal caramel in beers and soy sauces. Beer has positively charged proteins suspended in it, and soy sauce has a high salt content that requires the more salt-tolerant positive caramel color. 

Cooper, D. J. Husband, F. A. Mills, E. N. C. Wilde, P. J. Role of Beer Lipid-Binding Proteins in Preventing Lipid Destabilization of Foam. J. Agric. Pood Chem. 2002, 50, 7645-7650. 

The time course of protein-polyphenol haze development in many packaged clear beverages has a two-phase pattern (see, for example, Fig. 2.17). At first no observable change occurs for some time. After this, haze formation begins and follows an essentially linear development rate. This phenomenon has been reported in beer (McMurrough et al., 1992) as well as apple juice, grape juice, and cranberry juice cocktail (Siebert, 1999, 2006). 

Because proteins are involved in beer (Evans and Sheehan, 2002) and champagne foams (Senee et ah, 1999), and these are desirable properties, ultrafiltration is not a suitable treatment for these products. Adsorbents that indiscriminately remove protein are unsuitable for the same reason. 

At one time, broad spectrum proteolytic enzymes (mainly papain and bromelain) were widely used to delay or minimize haze formation in beer (de Clerck, 1969). The enzymes cleaved protein chains, that when... 

Asano, K., Shinagawa, K., and Hashimoto, N. (1982). Characterization of haze-forming proteins of beer and their roles in chill haze formation. /. Am. Soc. Brew. Chem. 40,147-154. 

It should also be kept in mind that the Beer-Lambert law often is not vahd at higher concentrations, since there occur interactions between chromophores and other molecules . This effect is observed especially at reading of proteins in the UV. The solvent may influence the absorbance too, because, for example, some of the aromatic amino acid residues are buried within hydrophobic core of the molecule and become exposed during unfolding of the protein when the composition of the solvent is changed or the protein is denaturated by dilution. 

The dyed proteins, though also not very cheap, are much more suitable from an economical point of view. The use of insoluble dyed proteins (e.g. hide powder azure) is very simple and handy. After the chosen reaction time the insoluble protein is removed by filtration or centrifugation and the absorbance of the filtrate is immediately measured. For instance, Rinderknecht proved that it was possible to determine trypsin activity with HPA (hide powder azure) in ng quantities per ml and proteolytic activities in biological materials, tissue extracts, serum, urine, faeces, etc. Other authors applied this substrate for assaying proteolytic activity in beer stabilized with chillproofing preparations containing proteases (mainly papain)... 

Protein haze in white wine thus differs in several aspects from protein haze in beer. It is well established that beer protein haze is due to interactions between proteins, derived from the barley storage protein hordein and rich in proline, and hop polyphenolic compounds (Bamforth 1999 Miedl et al. 2005 Siebert 1999 Siebert and Lynn 2003). White wine proteins are not derived from storage proteins of grape seed nor are they as rich in proline as hordein. In addition, wine protein haze formation cannot be eliminated by removing polyphenolic compounds by PVPP (Pocock et al. 2006) while in beer this has been applied as a commercial strategy (Leiper et al. 2005 Madigan et al. 2000). 

Kwon, S.W. (2004). Profiling of soluble proteins in wine by nano-high-performance liquid chro-matography/tandem mass spectrometry. J. Agric. Food Chem., 52, 7258 - 7263 Lee, T. (1986). Protein instability nature, characterization and removal by bentonite Leiper, K.A., Stewart, G.G., McKeown, I.P., Nock, T, Thompson, M.J. (2005). Optimising beer stabilisation by the selective removal of tannoids and sensitive proteins. J. 1. Brewing, 111, 118-127... 

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